Ch. 13 Extra +++

What is the primary source of water for the Colorado River, and how has it been modified for use?

The Colorado River primarily depends on snowmelt from the Rocky Mountains. Over the past century, it has been modified by 14 major dams, reservoirs, and canals to supply water for agriculture, cities, and industries in seven states.

What are the key benefits provided by the Colorado River's dam-and-reservoir system?

The system provides hydroelectric power to approximately 40 million people, supplies irrigation water for 15% of the nation's crops and livestock, and delivers drinking water to cities like Las Vegas, Phoenix, and Los Angeles, enabling them to thrive in arid regions.

What challenges does the overuse of the Colorado River highlight?

Overuse has led to severe drought conditions, with Lake Mead reaching record-low levels in 2015. This illustrates the difficulties of managing shared water resources in arid regions, exacerbated by population and economic growth, creating a major environmental challenge for the 21st century.

unique properties of water

- expands when frozen (ice floats on top of water, saving biological organisms below)

- exists as a liquid over a wide temperature range (doesn't freeze or boil away)

- dissolves compounds (flushes wastes, dissolves nutrients, dilutes wastes)

how is access to water a global health issue

many people don't have access to safe drinking water; lots of people die from waterborne infectious diseases (4,100 daily)

how is access to water an economic issue

produces food and energy, reduces poverty

- many of those who inhabit poor countries have to find water and carry it to their respective homes.

how is water a national and global security issue

increasing tensions within and between some nations over access to limited freshwater resources that they share.

how is water an environmental issue

excessive withdrawal of water from rivers/aquifers results in falling water tables, decreasing river flows, shrinking lakes, and disappearing wetlands.

only ____ of the planet's water supply is liquid freshwater (lakes, rivers + streams)

0.024%

atmospheric warming does what?

evaporates more water into the atmosphere, leaving wet places wetter and dry places drier. leads to intense floods and droughts.

zone of saturation

the lower zone where water accumulates between small rock particles.

how are aquifers replenished/recharged?

naturally by precipitation that sinks downward thru exposed soil + rock.

also from the side from nearby lakes, rivers, streams

use of groundwater

pumped to surface to irrigate crops and supply households/industries

problem with freshwater absorption

urban landscapes have been paved over, preventing absorption. in dry areas of the world (LA), there is little precipitation available to recharge aquifers.

deep aquifers (fossil aquifers)

filled with water by glaciers that melted thousands of years ago

surface water

freshwater from rain and melted snow that flows or is stored in lakes, reservoirs, wetlands, streams, and rivers.

surface runoff

precipitation that does not soak into the ground or return to the atmosphere by evaporation

drainage basin is also called what?

watershed

if we remove ____ in a particular location faster than it is replenished, nearby streams, lakes + wetlands can dry up.

groundwater (which begs the question: why is PV removing 112 million gallons of groundwater...)

reliable surface runoff

surface runoff of water that generally can be counted on as a stable source of water from year to year. increasing in arid climates

major uses of groundwater + surface frewshwater

cooling of electric power plants, irrigation, public water supplies, industry + livestock production.

how is the Colorado river affected

- Colorado River basin is located in some of the driest lands in the United States and Mexico.

- legal agreements between the United States and Mexico allocate more water for human use than the river can supply.

- because of the many dams installed along the Colorado River and the water that is diverted to cities and agricultural regions, the river has rarely flowed all the way to the Gulf of California.

- the river receives enormous amounts of pollutants from urban areas, farms, animal feedlots, and industries as it makes its way toward the sea.

virtual water

water that is not directly consumed but is used to produce food and other products.

freshwater scarcity stress

a measure based on a comparison of the amount of freshwater available with the amount used by humans

who faces water scarcity?

most countries in Middle East + Africa; 2/3 of China

why are water shortages a problem in the US

renewable freshwater isn't evenly distributed and a lot of it is polluted by agricultural and industrial waste.

land subsidence

the sinking or settling of land to a lower level in response to various natural and human-caused factors

sinkhole

extreme and sudden subsidence. once an aquifer becomes compressed, recharge is impossible.

San Joaquin Central Valley

overpumping of aquifers here to irrigate crops has caused half of the valley's land to subside by 1 to 28 feet.

groundwater ___ in coastal areas, causing what?

overdrafts: pulling saltwater into freshwater aquifers!

causes contaminated groundwater which is undrinkable and unsafe for irrigation.

how to prevent groundwater depletion

use water more efficiently, subsidize water conservation, limit # of wells, stop growing water-intensive crops in dry areas

control groundwater depletion

- Raise price of water to discourage waste

- Tax water pumped from wells near surface waters

- Set and enforce minimum stream flow levels

- Divert surface water in wet years to recharge aquifers

harmful impacts of over pumping aquifers

land subsidence, greater energy use in order to pump water from deeper depths, and saltwater intrusion in coastal areas.

dam

a structure built across a river to control the river's flow or to create a reservoir.

reservoir

artificial lake created when a stream is dammed

climate change impacts on dams

dmountain snows will melt faster and earlier, making less freshwater available to the river system when it is needed for irrigation during hot and dry summer months.

problems w/ desalination

1. high cost

2. pumping large volumes of seawater thru pipes and using chemicals to sterilize water and keep down algae growth kills many marine organisms and also requires large inputs of energy to run pumps

3. produces large quantities of salty wastewater that must go somewhere

how are glaciers critical to water supplies

glaciers accumulate and store water during the winter season and in the summer release the melt water into an adjoining river. as temperatures on earth warm and glaciers shrink, there is less water to feed river systems that people and ecosystems depend on.